Typically engine events are monitored using analog storage devices, i.e. oscilloscopes. The test engineer analyzes the cylinder and fuel injector pressure using an oscilloscope to determine engine performance. Unfortunately interpretation of the signals as viewed on the oscilloscope varies from one engineer to the next. Thus accurate analysis is dependent on the skill of the engineer to accurately use the oscilloscope and also on the accuracy of the oscilloscope. Due to human error, poor measurement repeatability results in poor accuracy.
One method to improve the above test procedure is using signal processing techniques that differentiate the cylinder pressure signal to determine the start of combustion. For example, under normal engine operating conditions, the cylinder pressure increases at the highest rate in response to combustion occurring in the cylinder. This method differentiates the cylinder pressure signal with respect to the crankshaft angle to determine the highest rate of cylinder pressure increase. It is supposed that the highest rate of cylinder pressure increase is associated with the start of combustion in the cylinder. However this does not always hold true. For example when the engine is under a heavy load, the cylinder pressure greatly increases during the compression stroke. Thus the greatest pressure increase may not be due to the start of combustion. Furthermore when the engine is retarded, combustion occurs after top dead center. Once again the highest pressure increase may not be associated with the start of combustion. Albeit such differentiation techniques are useful, they are; however, prone to produce inaccurate results.
The present invention is directed to overcoming one or more of the problems as set forth above.